Do your knees hurt when you go down stairs?
Do your knees ache when you sit to watch a movie?
Do you have difficulty getting up out of a chair after sitting?
Does squatting really hurt your knees?If the answer is yes to these questions, you may be suffering from Patellofemoral pain syndrome.
Patellofemoral Pain Syndrome can be described as pain under or around the kneecap (Patella). Young adult females are more often affected than males because a wider pelvis places increased stress on the knee joint.
BIOMECHANICS (How does the knee work?)
To understand the causes of the pain due to a tracking dysfunction, we must first understand the normal mechanics of the knee. The knee is made up of the femur (thighbone), the tibia (shinbone) and the patella (knee cap). The patella (knee cap) is a small triangular shaped bone which slides on the end of the femur. Large ligaments attach to the femur and tibia to provide stability. The long thigh muscles (quadriceps) give the knee strength. A smooth substance (articular cartilage) cushions the joint surfaces where these three bones (femur, tibia and patella) touch. This enables the bones to move with ease.
The knee cap functions to increase the force of straightening your leg (knee extension) by 50%. In doing so there is increased force placed on the joint. Here is an example; normally walking places a force of half of ones body weight on the knee joint, stair climbing places a force of 2.5 times ones body weight on the joint, descending stairs places 3.5 times ones body weight on the patellerfemoral joint and squatting places 7.5 times ones body weight on the joint.
The knee cap moves slightly up and down in a grove on the femur during bending and straightening on the knee (patella tracking). Patellar tracking dysfunction occurs when the knee cap is pulled off to the side (laterally) or to the outer aspect of the knee, as the knee is straightening under load. Various thing help keep the patella tracking well. These include: the quadriceps muscle which acts {See Figure1} as a stabilizer. The quadriceps muscle is made up of 3 parts; an inner (medial), outer (lateral), and central part. Good tracking requires that there is a balance in strength and flexibility between the inner and outer quadriceps. If the outer quadriceps muscle is stronger than the inner part then the knee cap has a tendency to be pulled laterally causing increased stress to the knee joint and its tissues.
You should know…
(1) Good flexibility in the lateral soft tissue structures such as the lateral retinaculum and iliotibial band. Tightness in either of these can cause the knee cap to track laterally.
(2) A normal angle of 13-18 degrees (q-angle) between the pull of the quadriceps muscle along the femur and the patellar tendon. An angle greater than normal causes greater force pulling the knee cap laterally. Factors which increase the q angle are A) a wide pelvis, B) flat feet and C) torsion in the femur.
(3) Normal structure of the knee cap and femur. The femur has a bump on its lower lateral (outer) aspect which helps stabilize the patella during bending and straightening of the knee.
If the bump is not large enough, the knee cap may have a tendency to move laterally, similarly a small knee cap which sits slightly higher on the femur and not in the groove has less stability and therefore may move laterally during straightening of the knee.
(4) Good strength in the hip abductor muscles is essential to help prevent excessive rotation in the femur during running. If the hip abductor muscles are week, then the femur will rotate inwardly placing increased stress on the knee joint.
TREATMENT AND PREVENTION
The treatment of patellar tracking dysfunction involves identifying the causes of the poor tracking and then correcting them. For example, if the inner (medial) part of the quadriceps muscle is weak causing the knee cap to be pulled laterally by a stronger lateral quadriceps, then one must strengthen the inner quadriceps. Moreover, if the hip abductors are weak causing excessive internal rotation of the femur, then one must strengthen the hip abductors. A physiotherapist can assess the problem and give the appropriate exercises specific to each individual.
If one wants to prevent pain due to tracking dysfunction, then the most important goal would be to maintain good strength, and flexibility in the all the leg muscles. As well, good shoes which help to absorb shock and promote good alignment will also aid in preventing pain from patellar tracking dysfunction.
Some key exercises which may help prevent patella femoral pain due to poor tracking include:
STRETCHING EXERCISES
1) Quadriceps stretch
2) Illiotibial band stretch
3) Hamstring stretch
STRENGTHENING EXERCISES
1) Quadriceps
- Non-weight bearing:
(i) isometric quadriceps
(ii) straight leg raising
- Weight bearing
(i) standing dips
(ii) lunges
(iii) step downs
(iv) wall sits
2) Hip abductor strengthening
BALANCE EXERCISES
1) Use of wobble board
2) Standing on one leg
Patellar Tracking Dysfunction often resolves with conservative treatment such as:
1)Physiotherapy: Specific exercises, manual therapy and modalities to enhance healing and reduce pain, and occasionally specific taping of the knee cap is required.
2) Education on proper foot wear.
3) Recognizing and correcting training errors., i.e. repetitive jumping or running too fast early in the season.
4) Initially restricting the aggravating activities.
5) Introduction of a modified exercise program to maintain cardiovascular fitness while preventing further pain and injury to the knee
6) A gradual re-introduction to the sports which stress the knee while maintaining a pain free status.
When conservative measures fail to resolve the pain and mechanical problems associated with patellar tracking dysfunction then a surgical approach is sometimes required.
In conclusion, Patellar tracking dysfunction is a common knee problem affecting many age groups and both recreational as well as elite athletes. One must remember it is just one cause of knee pain. There are many other causes of knee pain and therefore it is essential that individuals experiencing knee pain consult a medical professional to obtain a proper diagnosis; Indeed, a correct diagnosis is essential to provide the proper treatment and thus the best possible rehabilitation.
Susan Reive, B.Sc.P.T., M.C.P.A.
Ottawa Physiotherapist
